The present invention relates to a chucking repeat controller for a work machine with ATC., and more particularly relates to an apparatus capable of repeating chucking operation for prescribed times upon detection of unsuccessful chucking operation at a main spindle on a work machine such as a milling machine on which a tool holder on the main spindle is automatically replaced with a different and/or new tool holder standing by in a tool magazine by operation of a tool transfer arm assembly under control of a numerical control device.
On a work machine of the above-described type, the main spindle is internally provided with a drawing bolt which is driven, by a drive motor connected thereto, for normal and reverse rotation in order to fasten or release a tool holder. In combination with this chucking operation at the main spindle, the tool transfer arm assembly carries out horizontal turning and vertical reciprocal motions in order to remove a tool holder from the main spindle back to the tool magazine and to feed a different and/or new tool holder from the magazine to the main spindle for replacement purposes.
It is well known that the chucking operation at the main spindle occasionally ends in failure due to unexpected ill screw engagement between the drawing bolt in the main spindle and the tool holder carried by the tool transfer arm assembly. Such failure in chucking operation causes falling of the new tool holder whilst disenabling the further continuous operation of the work machine.
In order to avoid such unsuccessful chucking operation, it is proposed to raise accuracy in construction relating to the screw engagement between the drawing bolt and the tool holder. Such a proposal, however, cannot assure completely trouble-free chucking operation.
As long as no complete elimination of unsuccessful chucking operation is expectable, it is desirable as a second measure, that the result of chucking operation should be automatically detected and, upon detection of any unsuccessful chucking operation, same chucking operation should automatically repeated. Further, too much repeated failure in chucking operation is believed to indicate occurance of some fatal trouble in operation of the work machine in particular in the function of the main spindle including the drawing bolt and such a situation doubtlessly requires overall checking and maintenance of the work machine. From this point of view, it is also desirable that, when failure in chucking operation repeats in succession over a prescribed times, further operation of the work machine should automatically intercepted and, more fabourably, some audible and/or visible alarm should automatically generated for operators' attention.